What are the expected blood flow cytometry results in someone with localized amyloidosis?

Flow Cytometry Results in Localized Amyloidosis

In patients with localized amyloidosis, blood flow cytometry results are expected to be normal, with no evidence of clonal plasma cells or B-cells in the peripheral blood. 1

Distinguishing Localized vs. Systemic Amyloidosis

Diagnostic Features of Localized Amyloidosis

• Localized amyloidosis is characterized by Congo red-positive amyloid deposits confined to a single organ or tissue site without evidence of systemic involvement 1
• Most common sites include urothelial tissue (21%) and larynx (14%), but can affect any organ 1
• Negative serum and urine immunofixation electrophoresis is a defining characteristic of localized amyloidosis 1
• No evidence of clonal plasma cells in peripheral blood by flow cytometry 1

Laboratory Findings in Localized Amyloidosis

• Normal complete blood count without evidence of anemia 1, 2
• Negative serum protein electrophoresis (SPEP) and immunofixation 1
• Negative urine protein electrophoresis and immunofixation 1
• Normal serum free light chain ratio 1
• Normal coagulation parameters with thrombin-antithrombin complex levels <3.6 ng/mL, fibrinogen levels <355 mg/dL, and plasmin-α2-plasmin inhibitor complex levels <0.9 μg/mL 3

Contrast with Systemic AL Amyloidosis

Flow Cytometry Findings in Systemic AL Amyloidosis

• In systemic AL amyloidosis, flow cytometry of bone marrow (not peripheral blood) typically reveals:

  • Monoclonal plasma cells (CD38++CD19-CD56+) at significantly higher levels than controls 4
  • Abnormal plasma cell phenotype with varying maturation patterns 4
  • Potential immunotherapeutic targets (CD20, CD38, CD52, or SLAMF7) on malignant plasma cells 5

• Multi-parameter flow cytometry of bone marrow can identify underlying clonal lymphatic cells in 97% of systemic AL amyloidosis cases 5

Important Diagnostic Considerations

• Flow cytometry of peripheral blood is not typically diagnostic in either localized or systemic amyloidosis 6
• Bone marrow examination with flow cytometry is essential for diagnosing systemic AL amyloidosis but typically normal in localized disease 6, 1
• Definitive diagnosis of localized amyloidosis requires:
  • Congo red-positive biopsy of affected tissue showing apple-green birefringence under polarized light 1, 2
  • Negative serum and urine immunofixation 1
  • Absence of clonal plasma cells in bone marrow 1

Clinical Implications and Management

• Localized amyloidosis has excellent long-term outcomes with 10-year survival of 78%, comparable to the general population 1
• No progression to systemic disease has been documented in localized amyloidosis 1
• Initial laboratory evaluation to exclude systemic disease could be limited to serum and urine immunofixation in most patients 1
• Treatment typically involves local excision of amyloid deposits rather than systemic chemotherapy 1

Common Pitfalls to Avoid

• Misdiagnosing localized amyloidosis as systemic disease, leading to unnecessary systemic therapy 1, 2
• Failing to perform adequate testing to exclude systemic involvement 6, 1
• Overlooking the need for tissue biopsy with Congo red staining for definitive diagnosis 1, 2
• Relying solely on flow cytometry for diagnosis without correlating with histopathology 1, 5